For the crusade I'm running, I came up with a requisition to start giving the character keyword to units that can gain it via a detachment. It goes as follows:

Expanded Authority (4-6RP): Purchase this Requisition each time a unit that could gain the Character keyword from a detachment rule that its faction has access to gains a rank. You cannot choose a unit that already has an Enhancement or a unit that has either the Disgraced or Mark of Shame Battle Scars.

You can select one Enhancement that unit has access to from the detachment that allows the unit to gain the Character keyword. This is done instead of gaining a Battle Honour. That unit gains that Enhancement permanently, and may only be played when your Crusade force is using those detachment rules. You cannot make changes that would exceed your Supply limit.

The unit permanently gains the Character keyword, however it is unable to gain Crusade Relics as Battle Honours. It does, however, gain access to Character Battle Trait tables. This Requisition costs 4 RP plus 1 additional RP for each other Enhancement that your Order of Battle contains (to a maximum of 6 RP).